Researchers found India's numbers particularly interesting because even though it boasts the third-largest Muslim population, Muslims only comprise 13 percent of India's total population.

"Most people think of the Muslim world being Muslims living mostly in Muslim-majority countries," Brian Grim, the project's senior researcher, said. "But with India ... that sort of turns that on its head a bit."

Other numbers revealed by the report: Ethiopa, for example, has almost as many Muslims as Afghanistan. France also has one million more Muslims than the U.S.